(317) Leioptila annectans annectans Blyth.
THE SIKKIM CHESTNUT-BUMPED SIBIA.
Leioptila annectens annectens, Fauna B. I., Birds, 2nd ed. vol. i, p. 300.
This Sibia ranges from Sikkim to the extreme East of Assam, both North and South of the Brahmapootra, Manipur, Lushai Hills and the Chin Hills. This bird must be rare in Sikkim, where Stevens failed to come across it, but it is said to inhabit elevations between 4,000 and 6,000 feet. One specimen was obtained in the Miri-Abor expedition. We did not obtain it about Margherita, though it must occur there, but it certainly is found and breeds in the Naga Hills between 5,000 and 7,000 feet, perhaps higher. In the North Cachar Hills it is resident all the year round between 4,000 and 6,000 feet, but even there it cannot be called common, whilst in the adjoining Khasia Hills it is rare and very local, a few flocks frequenting the very dense, humid Rhododendron and Oak forests along the ridge known as “the Peak” at 6,000 feet.
I have never seen this bird in anything but the wet evergreen forests and, even in these, it must have some green undergrowth and, for breeding purposes, a sufficiency of small trees on which to place the nest. It is found well into the interior of such forests and not, as with so many birds, only near streams and the more open parts.
The nest is usually placed on a branch of a small tree between 8 and 20 feet from the ground, in most instances being built in a fork of an outer branch, slender and difficult to get at without breaking the eggs. In North Cachar the nests were built on small, non¬descript saplings in branches where they were easily visible, and no attempt seemed to be made by the birds to conceal them. In the Khasia Hills they were situated either in stunted Oaks, fairly well hidden, or in Rhododendrons. In these latter they were some¬times completely screened from view by the dense foliage, but they were also sometimes placed in a naked branch and fully exposed when thick patches of foliage were growing conveniently just alongside.
The nests are cup-shaped and very neatly and strongly built, with stout walls and well finished off finings. Roughly the nests vary between 5 and 7 inches in outward diameter and may be from 4 to 6 inches in depth, whilst the egg-cavity varies between 2 and
2 .1/2 inches across by nearly the same in depth. Outwardly the nest appears to be all moss but, if more carefully examined, it is seen to have a few leaves, a thread or two of fine grass and, almost certainly, a few moss-roots mixed with the moss ; inside the outer moss-wall there is a deep layer of grass, bamboo and other leaves and a few stems of weeds, well worked and twisted in together ; sometimes there are a few scraps of moss also, but this is dry, not green, as on the outer walls. The lining is of fine fibres, roots or rhizomorph. The bird is not shy but does not sit very close on the nest ; when, however, she leaves it she continues to fuss round close by, uttering a constant little “chirr-r-r,” which soon draws attention to the nest if it has not already been noticed.
The breeding season is May and June and I have taken no nest that I can remember in April or July.
They lay normally three eggs but, sometimes, two only and occasionally four, though this number is exceptional.
The eggs vary considerably but are quite typical of the Sibias. The most common type has the ground-colour a very pale blue grey or green-grey ; the primary markings consist of blotches and smears of reddish-brown, sometimes very pale, with a strong dark outline ; here and there are spots and short wavy lines of the same colour, while under these are secondary blotches and smudgy markings of pale lavender and pale brown. Generally the markings of both kinds are more numerous over the whole larger end but, occasionally, they are equally so everywhere. A second type is similar to this but has the ground a bleached yellowish-white or grey- blue white. A third type has the ground a bright pale blue, the markings restricted to a few very fine long lines of red-brown twisting here and there over the surface, in addition to which there are sometimes a few pale lavender spots. These latter eggs are just like miniature eggs of Actindodura, and it is interesting to note that an examination of a big series of the eggs of the various Sibias shows that nearly all aberrant eggs of one species can be matched by the normal eggs of another species.
One very beautiful clutch taken in the Khasia Hills contains two eggs more than usually heavily blotched, whilst another clutch of two is almost spotless.
In shape the eggs are moderately long ovals, generally well compressed towards the smaller end, which varies from normal to rather pointed.
Twenty-five eggs average 22.0 x 15.5 mm. : maxima 23.0 x 17.0 mm. ; minima 21.0 x 16.0 and 21.4 x 15.1 mm.
In most Sibias’ eggs the texture is fairly fine but not very close, and there is little or no gloss. The eggs of the Leioptila group are all rather fragile in proportion to the size of the egg, differing much in this respect from those of the Bar-wing, or Actinodura, group.
I have trapped both sexes on the eggs, so that it would appear that both assist in incubation. I have never seen a nest being built.
317. Leioptila annectans annectans
(317) Leioptila annectans annectans Blyth.